Recently, solid preparations disintegrating in the oral cavity which can be easily ingested by elderly people and children without water have been frequently developed because they are very convenient. The following known documents disclose such preparations.
Japanese Patent Application Laid-Open (JP-A) No. 2000-281564 (Patent Document 1) discloses an orally disintegrating tablet containing microgranules having an average particle diameter of 400 μm or less and an additive, wherein said granules are prepared by coating a composition containing 10% by weight or more of an acid-labile physiologically active substance with an enteric coating layer.
JP-A 2000-103731 (Patent Document 2) discloses a rapidly disintegrating solid preparation containing 1) an active pharmaceutical ingredient, 2) a sugar and 3) a low-substituted hydroxypropyl cellulose having 5% by weight or more to less than 7% by weight of a hydroxypropoxyl group.
JP-A 2003-081814 (Patent Document 3) discloses a method of producing a tablet which comprises tableting a coated particle containing a physiologically active substance at a temperature exceeding room temperature.
On the other hand, JP-A 10-036291 (Patent Document 4) discloses D-mannitol which can be used as an excipient excellent in moldability, and a method of producing the same.
The aforementioned known documents do not describe a method of producing an orally disintegrating solid preparation which comprises mixing microgranules containing an active pharmaceutical ingredient with an additive containing δ-mannitol and then tableting the mixture.    Patent Document 1: JP-A 2000-281564    Patent Document 2: JP-A 2000-103731    Patent Document 3: JP-A 2003-081814    Patent Document 4: JP-A 10-036291